So-called cut tobacco obtained by cutting tobacco leaves is used for usual tobacco articles such as cigarettes. In the step of cutting tobacco leaves or in other tobacco manufacturing steps, various types of tobacco waste such as leaf waste, cut waste, powder tobacco, or rib waste are produced. Conventionally, in order to effectively utilize such tobacco waste, it is bound to a suitable binder, and added with a reinforcing agent, a humectant, and the like. The mixture is extruded through a gap between a pair of rollers to form a sheet, and the sheet attached to the surface of one roller is separated therefrom with a doctor knife to obtain sheet tobacco (See Japanese Patent Publication No. 48-5919). The sheet tobacco is cut and mixed with normal cut tobacco and used as a raw material for cigarettes and the like.
When sheet tobacco manufactured in the above manner has wrinkles, it has considerable filling capacity (i.e., is bulky) when cut. Therefore, the amount of cut tobacco rolled as cigarettes can be reduced, resulting in economical advantages. In the above-mentioned method, when the sheet is separated by the doctor knife, wrinkles are formed in the sheet. However, as shown in FIG. 1, wrinkles formed in sheet tobacco in this manner are small wrinkles having a pitch of 0.1 to 0.2 mm and a height including the sheet thickness of about 0.2 mm when sheet tobacco having a thickness of 0.1 mm is used. Therefore, this sheet does not provide sufficient filling capacity when cut. Japanese Patent Publication No. 48-5919, mentioned above, discloses the use of a special doctor knife for forming large wrinkles. However, large wrinkles can be formed for only a short period of time due to wear on the doctor knife.